1. Field of the Invention
The present invention relates to a projection-type display device for projecting an image which is generated by an image generating device including a spatial light modulation element, and a cooling structure for the device.
2. Description of the Related Art
A projection-type display device using a digital micromirror device (DMD: trademark) as a spatial light modulation element has been already put into practical use.
In the projection-type display device, spatial modulation of light giving a predetermined color to the light from a light source by using filters of R, G, and B is executed by means of the DMD, and image light obtained by spatial modulation is projected for obtaining a display image.
Recently, a larger light source (a high output light source), and a uniform intensity distribution of light from a light source have been desired in order to meet requirements for increasing the size of a display image at the final step, and for obtaining a sharp image even in a bright room.
However, there has been a problem that uniformalization of light-intensity distribution causes a loss in the intensity of light to be used for the display image at the final step, and the higher output of the light source makes the calorific value increase.
Accordingly, a method in which air flow is supplied to the light source or the vicinity thereof for cooling has been adopted in many cases.
Jpn. Pat. Appln. KOKAI Publication Nos. 2000-330202 and 2002-318423, and U.S. Pat. No. 6,343,862 are well known patent documents disclosing a cooling technique for a projection-type display device.
Jpn. Pat. Appln. KOKAI Publication No. 2000-330202 has disclosed an example in which an airflow by which the optical system is cooled is discharged to the outside after passing through the inside of a power supply case.
Jpn. Pat. Appln. KOKAI Publication No. 2002-318423 has a description of heat dissipation of a light shield plate provided for controlling the influence of dust and the like in a mirror chamber in which an optical element is arranged.
U.S. Pat. No. 6,343,862 has illustrated an example in which, in order to realize the uniform intensity distribution of light from the light source, a light pipe is used.
Jpn. Pat. Appln. KOKAI Publication Nos. 2000-330202 and 2002-318423, which have both described a cooling technology, have not illustrated an optical element which is required to be cooled in a manner independent of that of the light source with a large loss, that is, uniformalization means, though the uniform light-intensity distribution can be realized by the cooling technologies.
U.S. Pat. No. 6,343,862 describes the uniformalization means, but does not refer to cooling.
Here, a cooling method, or a cooling device, which meets the requirements for the uniform light intensity in order to realize a high output light source, and a large display area, cannot be achieved even by combination of the technologies described in the above-described three documents, wherein the high output light source, and the large display area have been currently realized.